This invention relates to a lip seal ring for sealing rotary shafts or reciprocating piston rod-and-piston assemblies. The lip seal ring is of the type which has an elastomer sealing portion bonded by gluing or by vulcanization, to a housing ring or reinforcing ring made of a deformation-resistant material. Typically, such a construction may be used as a rod sealing ring for pneumatic springs and the like; it has an elastomer sealing lip portion and a face oriented away from the sealing lip portion and bonded to a reinforcing (stiffening) ring.
Elastomer lip seal rings used for sealing the piston rods in pneumatic springs are vulcanized to a metal disc at their radial end face oriented away from the sealing lip part, for an accurate positioning of the sealing lip and for stiffening to resist the substantial compression loads during operation. To instal the rod sealing ring, the latter is pressed onto the cylindrical rod guide of the pneumatic spring. The rod guide simultaneously serves as an end closure for the pneumatic spring tube. The elastomers of the rod sealing rings are preferably oil-resistant nitrile-butadiene rubbers or, at high temperature loads, fluoroelastomers, while for cylindrical rod guides preferably duroplastic synthetic materials ar used.
From the operational point of view it is of importance in sealing lip rings of the above-outlined type that a very firm bond be ensured between the elastomer and the housing or the stiffening part, particularly because of the large, alternating mechanical and thermal loads during operation and because of the corrosive sealing fluids that may be present. Because a rubber-to-metal or rubber-to-plastic bond is technologically difficult to achieve, in the manufacture of the lip seal rings the mutually adhering surfaces of the housing rings or stiffening rings have to be particularly carefully treated and sometimes coated with special adhering materials. These procedures render the manufacture of the lip seal rings complicated and expensive.
For simplifying the manufacture of elastomer rod sealing rings, the elastomer rod sealing ring portion is, according to German Patent No. 2,822,615, directly connected with the cylindrical rod guide so that an additional stiffening ring could be dispensed with. Such a solution however, still requires additional process steps for ensuring an optimal bond. Further, a pre-treatment of the adhering surfaces and the use of adhering means have been necessary and also, recesses as well as additional constructive measures had to be provided in separate process steps in the guide cylinder and/or the elastomer portion. Consequently, this solution has resulted in very few economic advantages--if any--in the manufacture of rod sealing systems.